Ink jet printing systems are known in which a print head defines one or more rows of orifices which receive an electrically conductive recording fluid from a pressurized fluid supply manifold and eject the fluid in rows of parallel streams. Printers using such print heads accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and depositing at least some of the drops on a print receiving medium, while others of the drops strike a drop catcher device.
In an ink supply system for an ink jet printer of the type shown in U.S. Pat. No. 4,399,446, clogging of the vacuum system downstream of the ink reservoir was observed during testing of the system. The clogging material appeared to be ink which entered the vacuum system, proceeded through the system to a restriction, dried in the restriction, and caused clogging.
This problem was exacerbated by a high degree of ink splatter in the ink reservoir in the area of the vacuum port, which is where much of the ink entering the vacuum port was believed to originate. Several attempts were made to solve this problem. One method for solving this problem was to install a baffle to prevent splattered ink from entering the vacuum port. However, clogging of the vacuum system still occurred, in spite of the effectiveness of the baffle in splatter control.
Another attempt to solve the clogging problem was to separate the suck dry vacuum and the system vacuum to isolate the two systems. Although no ink appeared to enter the system vacuum when this method was employed, clogging of the system vacuum still occurred. Upon further investigation, dried ink mist was unexpectedly discovered in a T-fitting connecting the ink reservoir to the system vacuum, and in a check valve in the system vacuum. The pattern of the build up in the check valve indicated that the clogging was caused by a gradual accumulation of ink mist which was dried by the continual flow of air through the system. Thus, a heretofore unknown problem of ink mist generation from an ink reservoir under vacuum was identified.
It is seen then that there is a need for an ink mist filter to collect mist and eliminate clogging of the system vacuum.